The present invention is related to optical signals, and more particularly to reducing a linewidth of an optical signal.
Compact lasers with narrow linewidth are known and used in applications such as coherent optical communication systems, portable and non-portable high resolution LIDAR systems, mm-wave and THz signal generation, optical imagers, optical phased arrays, sensing, opto-electronic oscillators, molecular and bio-molecular spectroscopy devices, and the like.
Commercially available Sub-KHz fiber laser linewidths have been achieved at the expense of weak tunability, large form factor, small wall-plug efficiency, and undesired mode hoping characteristic. Using a conventional feedback technique to cancel phase noise over a large frequency bandwidth often results in feedback loop instability because the laser is part of the feedback loop. Thus, the laser's characteristics such as its FM response may effect the loop performance such as the phase noise reduction bandwidth. Accordingly, a need continues to exist for an optical signal linewidth reduction system that overcomes the shortcomings of the conventional linewidth reduction systems.